Electric motor.



No. 655,268. I Patented Aug. 7, 1900. E. G. P. OELSCHLAGER &. G. 0. F. SCHR OTTKE. ELECTRIC MOTOR.

(Application filed Dec. 27, 1897.)

(In Model.)

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. rTED STATES ATENT QF-FICE.

ERNST GUSTAV PAUL OELSCHLAGER, OF CHARLOTTENBURG, AND CARL OTTO FRANZ SCI-IROTTKE, OF BERLIN, GERMANY, ASSIGNORS TO THE SIEMENS & IIALSKE ELECTRIC COMPANY OF AMERICA, OF CHICAGO,

ILLINOIS.

ELECTRIC MOTOR.

SPECIFICATION forming part of Letters Patent No. 655,268, dated August 7, 1900.

Application filed December 27, 1897. Serial No- 663,564. (No model.)

T0 to whom it may concern.-

Be it known that we, ERNST GUSTAV PAUL OELSOHLAGER, residing at Charlottenburg, and CARL Orro FRANZ ScnRorrKn, residing at Berlin, Germany, subjects of the Emperor of Germany, have invented new and useful Improvements in Electromotors, (Case No.42) of which the following is a specification, reference being had to the accompanying drawings, forming a part of this specification. Ourinvention relates to electric motors,and has for one of its objects the provision of means whereby injurious sparking at the motor is overcome when the motor is cut out of circuit.

A second object of the invention is to provide improved means whereby a braking action is exerted upon the armature of the motor when it is out out of circuit.

It is well known that'when motors are cut out of circuit while in operation by reason of induction a strong extra current is created. This extra current frequently interferes with the proper operation of the motor and often injures the same, since it is likely to pierce the insulation and cause heavy sparks which do great damage to the switches and often is the cause of shirt circuits. When the main circuit, whose connection with a shunt-machine is controlled by any switching apparatus now commonly in use, is opened, the current due to the interruption is insignificant, since the armature continuing to rotate furnishes current to the field. Consequently the field magnetism ceases gradually. It is necessary, however, in reversing the motor to interrupt this current,which ordinarily would cause a strong formation of sparks,which are repeated when the field-circuit is again closed by the pole-changing switch, the armature in the meantime rotating.

Generally speaking, our invention consists in providing a secondary path through the starting resistance for the extra current, whereby the injurious sparking is avoided.

The preferred embodiment of our invention consists in providing a path parallel to the field-windingof the motor, this path preferably containing a suitable amount of the starting-resistance. We also preferably employ the starting-resistance as a brake, the resistance being'included in circuit with the armature when it is to be reversed.

We will explain our invention more fully by reference to the accompanying drawings, which illustrate two embodiments thereof.

In the drawings, Figure 1 is a diagrammatic view of a shunt-machine and the apparatus of our invention associated therewith. Fig. 2 shows a slight modification of the apparatus illustrated in Fig. 1.

Like letters indicate like parts in both views.

The mains to a lead from any suitable source of current. A motor comprising an armature b and field-coils c c is adapted to be connected with or disconnected from the mains by the switch d. A pole-changing switch 8 is provided for reversing the rotation of the machine. We prefer to employ a resistance j, which is also the starting-resistance, in parallel with the coils c c, a switch g being provided, whereby the resistance is thrown into parallel circuit with the fieldcoils when the motor is to be disconnected. In the apparatus shown in Fig. 2 a portion of the starting-resistance is switched into the armature-circuit before circuit through the armature is opened.

The preferred operation of the apparatus shown in Fig. 1 may be generally described as follows: The current through the armature is first interrupted by the movement of switch 6, which may be done without much sparking. The switch 9 is then closed, the resistance. f being thereby switched into parallel with the shunt field-coils, the main current now being divided between the shuntcoils and the resistance. Main switch d is then opened, the main circuit traversing the coils c and resistance f being thereby broken. Any spark that results upon the interruption of the circuit, including the coils and resistance, will not be injurious. The switch g is next opened, the switch (1 is closed, and, finally, the pole-changing switch 6 is thrown completely to pass the current thron'gh the armature in a reverse direction.

In Figs. 1 and 2 the starting resistance or rheostat f performs the double function of a starting-rheostat and the resistance for pre venting the formation of injurious sparks.

In the apparatus shown in Fig. 2 the part of the starting resistance or rheostat between the points f f serves the triple purpose of the resistance about the field-winding, a portion of the rheostat, and also as a braking-resistance to be included in short circuit about the armature when the motor is cut out of circuit.

lVe do not wish to be limited to the employment of the entire starting-resistance in the secondary path about the field.

Changes may be made by those skilled in the art without departing from the spirit of this invention, and we do not, therefore, desire to be limited to the precise construction shown and described; but,

Having thus described our invention, what we claim as new, and desire to secure by Letters Patent, is-

1. The combination with a main circuit, of a motor, means for connecting the sanie in circuit with and disconnecting it from the said circuit, a pole-changing switch having suitable connections for reversing the polarity of the motor, said motor having a field-winding in shunt of the armature thereof, starting-resistance, a parallel path about the field-winding, and means for closing the same through said starting-resistance when the motor is to be cut out of circuit, whereby injurious sparking is avoided, substantially as described.

2. The combination with a main circuit, of a lnotorhavinga field-winding in circuit with the armature thereof and in series with the main circuit, starting-resistance, means for including the same in parallel with said fieldwinding between the sides of the circuit, and means for disconnecting the motor from the main circuit, substantially as described.

3. The combination with a main circuit, of a motor, means for connecting the same in circuit with and disconnecting it from the said circuit, a pole-changing switch having suitable connections with the armature for reversing the direction of current passing through the same, said motor having a fieldwinding in shunt of the armature thereof, starting-resistance, means for establishing a shunt-circuit about the field and including said starting-resistance in circuit with the shunt, and means for including starting-rcsistance in circuit with the armature, to act. as a brake, substantially as described.

4:. The combination with a main circuit, of a motor having a field-winding and an armature, starting-resistance adapted to be included in series with the armature-circuit of the said motor, a pole-changing switch, a secondary path about the field -winding, and means for closing said path through said start ing-resistance and opening the main circuit, substantially as described.

5. The combination with a main circuit, of a motor having a field-winding and an armature, means for connecting the same in circuit with and disconnecting it from the said circuit, starting-resistance adapted to be included in series with the armature-circuit of the said motor, a pole-changing switch, a secondary path about the field-winding, and means for closing the same through said starting-resistance when the motor is to be cut out of circuit, whereby injurious sparking is avoided, substantially as described.

6. The combination with a main circuit, of a motor having a field-winding, a secondary path about the field-winding, starting-resistance adapted for inclusion in series with the armature-circuit of the said motor, and means for including said resistance in said secondary path of the field-winding, thereby avoiding injurious sparking, substantially as described.

7. The combination with a main circuit, of a motor having a field-winding, a secondary pat-h about the tiel(l-winding,adj ustable starting-resistance adapted for inclusion in series with the armature-circuit of the said motor, and means for including said resistance in said secondary path of the fieldwvincling, thereby avoiding injurious sparking,substantially as described.

In testimony whereof we aftix our signatures in the presence of two witnesses.

ERNST GUSTAV PAUL OELSCHLltGllll. CARL OTTO FRANZ SCHROTTKE. lVitnesses:

CHARLES H. DAY, PAUL SUEIJER. 

